/*
 * Copyright 2017 Gabor Varadi
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.zhuinden.simplestack;

import java.util.Map;

import javax.annotation.Nonnull;

/**
 * A default strategy that clears the state for all keys that are not found in the new state.
 */
public class DefaultStateClearStrategy
        implements Backstack.StateClearStrategy {
    @Override
    public void clearStatesNotIn(@Nonnull Map<Object, SavedState> keyStateMap, @Nonnull StateChange stateChange) {
        CollectionHelper.retainAll(keyStateMap.keySet(), stateChange.getNewKeys()); // see #256
    }
}
